The present invention relates to a new and distinct hybrid of Allium hybrid plant named ‘Windy City’ characterized by dark green foliage in combination with purple-violet flowers, on semi-sterile plants. The new Allium hybrid was the result of a breeding program taking place in Hebron, Ill. since 2010. ‘Windy City’ arose as a selection from seed sown from open pollination of unnamed plants of Allium. The exact parentage of Allium hybrid ‘Windy City’ is unknown, however the female or seed parent is believed to be Allium hybrid ‘Summer Beauty’, while the male pollen parent is unknown. The selection of the new plant was due to its' dark green foliage in combination with purple-violet flowers, on semi-sterile plants. Asexual division propagation has been the means of reproduction. The initial cutting and division propagation has taken place at a nursery in Hebron, Ill. in 2011. The new Allium has shown to be stable and identical in reproduction to the parent after dividing over 5000 plants from 2011 to 2015.